Concealed weaponry, especially of this type, would probably be frowned upon my most LEOs and rangers. Looks up your local laws on cane-swords, tube projectiles and the like.
If you're wanting to hunt, you'll do better by just trapping rather than trying to make a bungee/spring launcher with a blade.
Springloaded things tend to fire off an inopportune times, as well, unless they're heavily reinforced (which isn't light, either.)
If it were me (and I was not in CA where it's illegal) I'd use it as a blowgun with a paralytic rather than going for a kinetic kill.
Or put a base/hook on it for an atlatl.
And, in case you care, with an arrow/crossbow-bolt you don't need a lot of KE to make a kill on small game.
Or bore small holes for music or a pipe if you're into that kind of thing. :P